In preliminary work, mRNA species coding for H2-I and HLA-D region coding sequences have been identified using an in vitro mRNA translation system. The poly-A rich mRNA encoding these sequences is in the 12 to 14S fraction, and this fraction has been used to make cDNA copies which have been cloned into pBR322. Two sources of B lymphocyte cDNA have been utilized: the human lymphoblastoid B cell line, CA, and a mouse B cell tumor line, CH-1. Four thousand clones of the human B cell cDNA sequences and approximately 4,000 clones of the CH-1 cDNA sequences are being screened using the following cDNA probes: (a) cDNA produced from the mRNA used for cloning from B cells, (b) cDNA produced from the human T cell line, molt-4 and a mouse T cell thymoma, (c) DNA sequences encoding mouse Mu and Kappa immunoglobulin heavy and light chains; and, (d) cDNA produced by extension of elevenmers homologous for specific sequences of the human p34 and murine EAlpha proteins. The research described in this proposal is designed to identify cDNA clones encoding H2-I and HLA-D region sequences and to use these to isolate and purify mRNA for production of new cDNA clones as well as to isolate genomic DNA clones. These will be used to analyze the genetic organization of the H2-I and HLA-D regions, to determine the number of gene repeats, to determine the complete sequence of the cDNAs encoding H2-I and HLA-D region gene products, and to isolate adjacent genomic DNA which may code for genes and gene products expressed at low levels below current methods of detection.